The present disclosure generally relates to a catalytic converter substrate structure, such as the type that can be used as a catalyst carrier in an exhaust gas purification apparatus for an internal combustion engine.
Catalyst carriers for exhaust gas purification apparatuses have conventionally employed a honeycomb structural body, wherein partition walls or intersecting walls are arranged in a honeycomb fashion to form multiple cells. An exhaust gas purification function is achieved by providing an exhaust gas purifying catalyst on the surface of the partition walls of the honeycomb structural body. For example, a wash coat and precious metals can be received on the substrate structure. The substrate structure gives the shape and much of the flow properties to the catalyst.
In conventional catalytic converters, the substrate structure typically defines cells that are uniformly sized. A problem with this arrangement is that uniform flow, which is desired for full utilization of the catalyst, cannot always be achieved when catalytic converter cases having varying shapes are employed. For example, some catalytic converter cases include a sharp bend or elbow. Others include an expansion portion that distributes flow from a small diameter passage to a relatively large catalyst substrate body. When uniform cells are used in these types of converter configurations, uniform flow is difficult to achieve. This can lead to inefficient operation of the converter. In addition, the non-uniform deterioration of catalyst causes one portion of the catalyst to deteriorate more quickly than other portions leading to premature failure of the converter.